Lubricating oil compositions containing metal dithiophosphate-nu-dialkylaminoalkyl alkenyl succinimide blends



United States Patent LUBRICATING OIL COMPOSITIONS CONTAINING METAL DITHIOPHOSPHATE N DIALKYLAMI- NOALKYL ALKENYL SUCCINIMIDE BLENDS Robert G. Anderson, Novato, Frank A. Stuart, Orinda, and Alan Y. Drummond, Richmond, Calif., assignors to California Research Corporation, San Francisco, Calif a corporation of Delaware No Drawing. Filed Mar. 15, 1960, Ser. No. 15,063

4 Claims. (Cl. 252-32.7)

This invention pertains to lubricating oil compositions containing N-dialkylaminoalkyl alkenyl succinimides as detergents.

This application is a continuation-in-part of patent application Serial No. 835,390, filed August 24, 1959.

Alkenyl succinie anhydrides and numerous derivatives thereof are Well known in the art. For example, alkenyl suceinic anhydrides in which the alkenyl radical contains from 5 to 20 carbon atoms are taught as corrosion inhibitors in lubricating compositions. Also, products obtained by reacting such alkenyl succinic anhydrides with monoamines are taught as ferrous corrosion inhibitors for lubricating oil compositions.

However, the above known alkenyl succinimides are not useful as detergents for lubricating oil compositions. in contrast thereto, the alkenyl succinimides described herein are useful as detergents in lubricating oil compositions.

Present day internal combustion engines operate at high speeds and high compression ratios. When used in the so-called city stop-and-go driving, which includes the greater part of the driving condition for a large percentage of todays automobiles, the internal combustion engines do not reach the most efficient operating temperature. Under city driving conditions, large amounts of partial oxidation products are formed, and reach the crankcase of the engine by blowing past the piston rings. Most of these partial oxidation products are oil insoluble, tending to form deposits on the various operating parts of the engine, such as the pistons, piston rings, etc. For the purpose of preventing the deposition of these products on the various engine parts, it is necessary to incorporate detergents in the lubricating oil compositions, thus keeping these polymeric products highly dispersed in a condition unfavorable for deposition on metals.

For the most part, the various detergents which are added to crankcase oils to reduce this formation of sludges and varnishes are metal organic compounds, particularly those compounds wherein the metal is linked to an organic group through an oxygen atom. Although these metalcontaining organic compounds have some effectiveness as detergents for dispersing the precursors of deposits within the oil itself rather than permitting them to form added deposits on the engine parts, they have the disadvantage of forming ash deposits in the engine. These ash deposits lower engine performance by fouling the spark plugs and valves and contributing to preignition.

It is a particular object of this invention to set forth lubricating oil compositions which are compounded with metal-free detergents.

It is a further object of this invention to provide lubricating oil compositions which are compounded with metal-free detergents whose detergency characteristics are enhanced by the presence of a synergist.

Therefore, in accordance with this invention, it has been discovered that lubricating oil compositions particularly useful for heavy duty service are obtained by incorporating metal dithiophosphates in lubricating oil compositions containing N-dialkylaminoalkyl monoalkenyl succinimides.

The N-dialkylaminoalkyl alkenyl succinimides are particularly efiective as detergents in lubricating oil compositions. By the use of lubricating oil compositions containing metal dithiophosphates and alkenyl succinimides, diesel and gasoline engine parts remain remarkably free of deposits and varnish even under severe operating conditions.

The N-dialkylaminoalkyl monoalkenyl succinimides wherein the alkenyl radical contains from 30 to 200 carbon atoms, and wherein said dialkylaminoalkyl radical contains a total of 3 to 10 carbon atoms, can be represented by the formula:

o R-oH-o R \NR-N/ Bro; n

wherein R is an alkenyl radical containing from 30 to 200 carbon atoms, R is a divalent alkylene radical, and R and R are alkyl radicals. The sum of the carbon atoms in the R, R and R is from 3 to 10; that is, R, R and R contain a total of no more than 10 carbon atoms.

It is particularly preferred that R is a polymer of an olefin containing from 2 to 5 carbon atoms, wherein the polymer has a molecular weight from 400 to 3000, more particularly from about 900 to about 1200. Such olefins are exemplified by ethylene, propylene, l-butene, 2- butene, isobutene, and mixtures thereof. Since the methods of polymerizing the olefins to form polymers thereof is immaterial in the formation of the new compound described herein, any of the numerous processes available can be used therefor.

R alkylene radicals include the divalent ethylene radical, propylene radical, butylene radical, etc. R and R alkyl radicals include methyl, ethyl, propyl, etc. It is particularly preferred that R contains 3 carbon atoms, and that R and R each contain 1 carbon atom.

Amine reactants for the formation of N-dialkylaminoalkyl alkenyl succinimides include dimethylaminomethylamine, dimethylaminoethylamine, dimethylaminopropylamine, dimethylaminobutylamine, dimethylaminoheptylamine, diethylaminomethylamine, diethylaminopropylamine, diethylaminoamylamine, dipropylaminopropylamine, methylpropylaminoamylamine, propylbutylaminoethylamine, etc. in can be described generally by the following equations, wherein a polyolefin is reacted with maleic anhydride to form a monoalkenyl succinic anhydride, which, in turn, is then reacted with a dialkylaminoalkylarnine to form an N-dialkylaminoalkyl monoalkenyl succinimide. Using a polymer of isobutene as an example of the alkenyl 300 F. to 450 F. "Because of the greater yield obtained I I radical, and dimethylaminopropylamine to exemplify the dialkylaminoalkylamine, these equations are as follows:

The above reaction between a polyolefin and maleic 'fanh'ydride is an uncatalyzed addition reaction which "should not be confused with a copolymerization reaction ,7 such as that obtained with a vinyl monomer and maleic anhydride. While the general reaction of an olefin and Equation H hereinabove, the reactants are used in such proportions and the reaction conditions are such that an imide is formed, not a diamide.

The reaction set forth'and described by Equation I hereinabove can proceed in a mol ratio of the polyolefin' to the maleic anhydride of. 1:1 to 1:10; preferablyfrom The reaction temperature can vary from thereby, it is-prefer red to use the higher temperature range (e.g 375 F. to 450 F.).

In the second step of the'reacti'on as exemplified by Equation 11 hereinabove, the yield of the imide is ex- I tremely'high even though the reactants are used in equal molar ratios.

The reaction described by Equation H hereinabove can be made'at 220 F., to 500 1F., preferably from 300 F. to 400'F. The alkenyl succinic anhydride and the polyamine are reacted in about equal molar quantities. An excess of amine can be used, and the unreacted amine removed by distillation.

Since the reaction between the polyolefin and maleic anhydride may not go to completion, the resulting alkenyl succinic anhydridemay contain some unreacted polyolefin. As it may not be desirable to separate out this unrea'cted polyolcfin at this stage, the resulting imide formed by'reaction of the alkenyl succinic anhydride and the diamine will contain this polyol efin as an impurity which can be a diluent in the formation of lubricating oil compositions. However, if it isso desired, this unreaCted polyolefin can be removed by precipitation, for

example, by acetone 'or methanol from a hydrocarbon solution. V

The metal dithiophosphates are metal salts of esters of dithiophosphoric acids represented 'by the following formula:

wherein R and R may be alkyl, aryl, alkaryl or aralkyl, hydrocarbon radicals containing a total of from 7 to 50 carbon atoms and M is a divalent metal. It is preferred that the R radical contains from 1 to 25 carbon atoms,

and that the R radical contains from Ste 25 carbon atoms. R and R may or may not be identical. Because of the improved synergistic effects obtained thereby, it is particularly preferred that R and R are dissimilar alkyl radicals.

When R and R are identical and consist ofthe lower molecular weight hydrocarbon radicals (e.g., butyl radicals), the metal salt normally does not have sufiicient oil solubility to permit its use in lubricating oil compositions. However, when the R and R are diiferent but still of low molecular weight (e.g., when R is a butyl radical and R is a pentyl radical), it is possible to prepare metal salts of mixed esters of dithiophosphoric acids which are sufiiciently oil soluble to inhibit the oxidation of the lubricating oil composition. The advantages of the use of low molecular weight R andR' groups also include the decreased cost overthat of the high'molec- Thus, in the practice of this invention, it is preferred to use metal salts of mixed esters of dithiophosphoric acids wherein R is derived from an alcohol containing no more than 4 carbon atoms; for example, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, sec-butyl alcohol, tertiary butyl alcohol, etc.; and wherein R is derived from alcohols containing from 5 to 18 carbon atoms including pentyl alcohol, hexyl alcohol, methylisobutylcarbinol, methylisopropylcarbinol, heptyl alcohol, isoheptyl alcohol, Z-ethylamyl alcohol, octyl alcohol, isooctyl alcohol, 3-ethylhexyl alcohol, 2-propylamyl alcohol, decyl alcohol, undecyl alcohol, 'dodecyl alcohol, hexadecyl alcohol, octadecyl alcohol, etc.

Examples of R and R when these are the same include the following radicals: octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, hexylphenyl, decylphenyl, dodecylphenyl, hexadecylphenyl, octadecylphenyl, etc.

Divalent metals of the dithiophosphates include the alkaline earth metals such as calcium, barium and strontium, and zinc. It is preferred that the metal is zinc.

The esters of dithiophosphoric acids used in the preparation of the metal salts of this invention include butyl pentyl dithiophosphoric acid, butyl hexyl dithiophosphoric acid, methyl hexyl dithiophosphoric acid, ethyl hexyl dithiophosphoric acid, butyl methylisobutylcarbinol dithiophosphoric acid, butyl heptyl dithiophosphoric acid, butyl decyl dithiophosphoric acid, butyl isoheptyl dithiophosphoric acid, butyl octadecyl dithiophosphoric acid, dioctyl dithiophosphoric acid, diheptyl dithiophosphoric acid, dihexadecyl dithiophosphoric acid, dioctadecyl dithiophosphoric acid, didectylphenyl dithiophosphoric acid, etc.

Lubricating oils which can be used as base oils for lubricating oil compositions of such alkenyl succinimides include a wide variety of lubricating oils, such as naphthenic base, parafiin base, and mixed base lubricating oils, other hydrocarbon lubricants, e.g., lubricating oils derived from coal products, and synthetic oils, e.g., alkylene polymers (such as polymers of propylene, butylene, etc., and the mixtures thereof), alkylene oxide-type polymers (e.g., alkylene oxide polymers prepared by polymerizing the alkylene oxide, e.g., propylene oxide, etc., in the presence of water or alcohols, e.g., ethylene alcohol), dicarboxylic acid esters (e.g., those which are prepared by esterifying such dicarboxylic acids as adipic acid, azelaic acid, suberic acid, sebacic acid, alkanol succinic acid, fumaric acid, maleic acid, etc., with alcohols, such as butyl alcohol, hexyl alcohol, Z-ethylhexy alcohol, dodecyl alcohol, etc.) liquid esters of acids of phosphorus, alkyl benzenes, polyphenyls (e.g., biphenyls and terphenyls), alkyl biphenyl ethers, polymers of silicon (e.g., tetraethyl silicate, tetraisopropyl silicates, tetra l-methyl- 2-tetraethyl) silicate, hexyl (4-methyl-2-pentoxy) disiloxane, poly(methyl) siloxane, and poly(methylphenyl) siloxane), etc.

The above base oils may be used individually or in combinations thereof, wherever miscible or wherever made so by the use of mutual solvents.

As lubricating oil additives, these alkenyl succinimides can be used in amounts of 0.1% to 80%, by weight, preferably 0.25% to 8%, by Weight.

The metal dithiophosphates are used in amounts of 5 millimols to 35 millimols per kilogram (i.e., 5 mM./ kg. to 35 mM./kg.) of finished product based on the metal content, preferably mM./kg. to 18 mM./kg.

The succinimides and the metal dithiophosphates are used in certain mol ratios with respect to each other. The succinimide-dithiophosphate mol ratio ranges from about 1:20 to about 10:1; preferably from 1:10 to 6:1, more preferably, 1:2 to 3:1. That is, the succinimide dithiophosphate mol ratio has values from 0.05 to 10, preferably 0.1 to 6, more preferably, 0.5 to 3.0.

The preparation of N-dialkylaminoalkyl monoalkenyl succinimides is illustrated in the following examples.

Example I.-Preparati0n of polybutenyl succinic anhydride A mixture of 1000 grams (1 mol) of a polybutene having a molecular weight of about 1000 and 98 grams (1 mol) of maleic anhydride was heated at 410 F. in a nitrogen atmosphere with agitation for a period or" 24 hours. The reaction mixture was cooled to 150 F, and 700 cc. of hexane added; after which the mixture was filtered under vacuum. After vacuum distillation to remove the hexane from the filtrate, the product was maintained at 350 F. at an absolute pressure of 10 mm. Hg for one hour to remove traces of maleic anhydride. The crude polybutenyl succinic anhydride thus prepared had a saponification number of 79.

Example H.Preparari0n of N-dimethylaminopropyl polyblztenyl succinimide A mixture of 21.3 grams (0.21 mol) of dimethylaminopropylamine and 150 grams (0.09 mol) of the polybutenyl succinic anhydride of Example I hereinabove, was blended with agitation in a nitrogen atmosphere, and the mixture was heated at 500 F. for a period of one hour, after which the absolute pressure was reduced to about 200 mm. Hg at this temperature during a period of 30 minutes to facilitate the removal of Water and excess amine. The reaction mixture was then allowed to reach room temperature at this reduced pressure. The reaction product contained 1.7% nitrogen (theory=1.8%). The identity of the N-dimethylaminopropylalkenyl succinimide was established by means of infra-red spectroscopy.

Table I hereinbelow presents further data concerning the preparation of N-dialkylaminoalkyl alkenyl succinimides. The polyamine was dimethylaminopropylamine, and the alkenyl radical on the alkenyl succinimide was 6 a polybutene, the molecular weight of which is noted in Table I.

1 Polyisobutenyl succinic anhydride.

Table II hereinbelow sets forth data showing the synergistic effect obtained by the combination of metal dithiophosphates and N-dialkylaminoalkyl monoalkenyl succinimides as lubricating oil additives.

The succinimide used was an N-dimethylaminopropyl alkenyl succinimide wherein the alkenyl radical had a molecular weight of approximately 1000, which alkenylradical was a polymer of isobutene.

The dithiophosphate was a zinc salt of a mixed dialkyl dithiophosphate wherein one of the alkyl radicals contained 4 carbon atoms and the other alkyl radical contained 5 carbon atoms.

The base oil was an SAE 10 base oil.

The data were obtained in a Caterpillar L-l test under Supplement I conditions for a period of hours as described in the Coordinating Research Council Handbook, January 1946.

The PD Nos. refer to the piston discoloration rating. After the engine test, the three piston lands are examined visually. To a piston land which is completely black is assigned a PD number of 800; to one which is completely clean, a PD number of 0; to those intermediate between completely black and completely clean are assigned PD numbers intermediate in proportion to the extent and degree of darkening.

1 These test results were obtained in a Caterpillar L-1 test under MIL-B2104 conditions. Thus, under the more severe supplement I conditions, these PD numbers would be considerably higher.

Tables III and IV hereinbelow present further data emphasizing the synergistic effects of the succinimidedithiophosphate combination as described herein.

The base oils and the succinimide were the same as described hereinabove for Table II.

Dithiophosphate A was a zinc salt of a mixed dialkyl dithiophosphate wherein one of the alkyl radicals contained 4 carbon atoms, and the other alkyl radical contained 5 carbon atoms; and dithiophosphate B was a zinc salt of a di(alkylphenyl) dithiophosphate wherein the alkyl radicals were derived from propylene polymers having an average of 12-14 carbon atoms.

The piston varnish rating is a visual observation of the amount of varnish on a piston skirt, with 10 being the maximum rating for a perfectly clean piston and a 0 being the rating of a piston fully covered with black varnish. This piston varnish rating correlates with road performance in auto-mobiles. This FL-2 test was made as follows:

A 6-cylinder Chevrolet engine was operated at 2500 rpm. for a period of 40 hours. This test is fully described in a Coordinating Research Council bulletin titled Research Technique for the Determination of the Eifects of Fuels and Lubricants on the Formation of TABLE III Additive E F G H Succinirr'ide, Wt. percent 0. O 0.0 1.0 1.0 Dithiophosphate A, mMJkg 12 0 12 Test Results:

Piston Varnish Ratings 2. 9 2. 9 6. 2 7 5 TABLE IV Additive I I K L M N Succinimide, Wt. percent 0.0 0.0 0. 0 1,0 1.0 1.0 Dithiophosphate A, mM./kg. O 12 0 0 6 l0 Dithiophosphate B, mlVL/kg.. 0 0 12 12 6 2 Test Results:

Piston Varnish Ratings 2. 9 2. 9 2. 9 9.8 7. 7 7, 4

It is readily seen from the data set forth hereinabove that lubricating oil compositions containing metal dithiophosphates and the succinimides described herein are markedly effective for the lubrication of internal combustion engines.

In addition to the dithiophosphates described hereinabove, lubricating oil compositions containing the N- dialkylaminoalkyl alkenyl succinimides of this invention may also contain other detergents, viscosity index improving agents, rust inhibitors, oiliness agents, grease thickening agents, etc.

We claim:

' l. A lubricating oil composition consisting essentially of an oil of lubricating viscosity, and from about 0.1% to 80% by weight of an N-dialkylaminoalkyl monoalkenyl suocinimide of the formula wherein R and R alkyl radicals containing a total of 7 to 50 carbon atoms, and wherein the succinimide-dithiophosphate mol ratio is from about 1:2 to about 3:1.

2. A lubricating oil composition consisting essentially of an oil of lubricating viscosity, and from about 0.1% to about 80%, by weight, of an N-dialklaminoalkyl monoalkenyl succinimide of the formula 0 ROHC R NR'-1v CH -O I R3 wherein R is a polyolefin' radical derived from a polymer of an olefin containing from 2 to 5 carbon atoms, said polymer having a molecular weight in the range of about 400 to about 3000, R, R and R are hydrocarbon radicals containing a total of 3 to 10 carbon atoms, and in combination with said succinimide from about 5 rnMJkg, to

8 about 35 rnM./kg. of a metal dithiophosphate of formula s ROl S Zn wherein R is an alkyl radical containing from 1 to 4 carbon atoms, and R is an alkyl radical containing from 5 to 18 carbon atoms, wherein the succinimide-dithiophosphate mol ratio is from about 1:2 to about 3:1.

3. A lubricating oil composition comprising a major proportion of an oil of lubricating viscosity, from about 0.25% to about 8%, by weight, of an .N-dialkylaminoalkyl monoalkenyl succinimide of the formula wherein R is a polyolefin radical derived from a polymer of an olefin containing from 2 to 5 carbon atoms, said polymer having a molecular weight in the range of about 900 to about 1200, R, R and R are hydrocarbon radicals containing a total of 3 to 10 carbon atoms, and in combination with said succinimide from about 5 mM./ kg. to about 35 inM/kg. of a metal dithiophosphate of the formula wherein R is an alkyl radical containing from 1 to 4 carbon atoms, R is an alkyl radical containing from 5 to 18 carbon atoms, and wherein the succinimide-dithiophosphate mol ratio is from about 1:2 to about 3:1.

4. A lubricating oil composition comprising a major proportion of a petroleum lubricating oil, from about 0.25% to about 8%, by weight, of an N-dimethylaminopropyl monoalkenyl succinimide of the formula R-CH-C CHZ-C 0 wherein R is a polyolefin radical having a molecular weight of about 1000, and from about 12 mM./kg to about 18 mM./kg. of a metal dithiophosphate of the formula wherein R is an alkyl radical containing no more than 4 carbon atoms and R is an alkyl radical containing from 5 to 18 carbon atoms, wherein the succinimide-dithiophosphate mol ratio is from about 1:5 to about 3:1.

References Cited in the file of this patent UNITED STATES PATENTS 2,364,284 Freuler Dec. 5, 1944 2,689,220 Mulvany Sept. 14, 1954 2,838,555 Goldsmith June 10, 1958 2,849,398 Moody et al Aug. 26, 1958 2,892,783 Stuart et al June 30, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,,Ol8 2 47 January 23 1962 Robert G, Anderson et alq It is hereby certified that error ep peers in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 22 line 58 after "etc."

insert The preparation of monoalkenyl succinimides here'- as the beginning of a new paragraph; column 7 line 54 after "R" insert are Signed and sealed this 5th day of June 1962;

(SEAL)- Attest:

ERNEST w. SWIDER A IDL-LADD Attesting Officer Commissioner of Patents 

1. A LUBRICATING OIL COMPOSITION CONSISTING ESSENTIALLY OF AN OIL OF LUBRICATING VISCOSITY, AND FROM ABOUT 0.1% TO 80% BY WEIGHT OF AN N-DIALKYLAMINOALKYL MONOALKENYL SUCCINIMIDE OF THE FORMULA 